metamatrials question?

hi all,why the band width of ebg(mushroom,peano,etc) determination of phase figure from -90 to 90 degree,not from -180 to 180,also why some cells from -45 to 45 pls reply methanks,regards

what do you mean by the band width of ebg determination of phase figure?
would you pls show a figure here?
BTW, previously i remembered once you replied my post. Contact me for further discussion and communication if you like. i'm also a newbee in metamaterials, antenna...

here figure,my question is clear now?

I think that it is agreed by consent for the range of merit, btw, like the pic attacked, we can't detemine the range between (-180 ; 180) coz it is whole work's range. Wait for more explains..